Analysis and Definition of Restoration Strategies with H-BIM Applications. The Case Study of Vittorio Giorgini's “Casa Esagono” in Baratti, Italy

This paper presents a research study on the “Casa Esagono”, realized in 1957 in Baratti (LI, Italy) by Vittorio Giorgini, aimed to lay the foundations for a restoration plan of this experimental wooden architecture, which is now in precarious conditions due to its location near the sea. The study was developed under a research agreement between DESTEC University of Pisa and the Municipality of Piombino, with the collaboration of B.A.Co. The historical analysis focused on the house and the figure of the non-conformist architect. On this basis, the geometric survey was developed for a representation in scale 1:25 plus architectural details. The building components were subjected to visual analysis, aimed to identify materials and types of deterioration. A conservation approach was finally proposed with the aim to maintain as much of the original elements, while increasing their durability in the coastal environment. The contribution will describe the workflow for the implementation of the H-BIM model, conceived for organ-ising all the data deriving from the historical and onsite research, and the restoration programme. The acronym H-BIM (Historic Building Information Modelling) is a recently created term to identify the application of BIM modelling, widely used for designing new buildings, to any project or intervention concerning the architectural heritage [1, 2, 3]. The development of a parametric model, created using a BIM software, allows different types of data to be associated with the modelled elements. This step is called “computerisation” of the model. By using H-BIM, it is possible manage and organise effectively all the needed information relating to the entire life of a historic building, which must necessarily be considered to define the restoration project, as well as during the restoration works. In this way, all the expert professionals involved in the restoration process can easily access the data and constantly update any information, a characteristic which turns to be particularly useful for the ongoing monitoring of the site conditions and for developing and managing a preventive maintenance plan. The methodology to develop an H-BIM model, also applied to the case study, includes the following phases: the documentary research aimed at obtaining information about the project, such as history and construction aspects; the geometric survey, the analysis of materials and current conditions; and, finally, the BIM modelling through dedicated software with subsequent computerisation and management of the model.

The multi-faceted architect Vittorio Giorgini has dedicated his life to the experimental investigation of forms linked to nature. His studies “were focused on building techniques capable of producing housing solutions that were efficient, functional, suited to the needs of everyday life and economically viable” [4]. Giorgini coined the term “Spatiology” to define his studies, meaning “the study of space naturally with the basis of that morphology which was taught by nature and which could not be accepted by the culture of the time” [5]. The account of his passionate research will flow into the book “Spatiology. The morphology of the natural sciences in architecture and design” [6].

In 1957, he graduated in Architecture in Florence, where he carried out professional and teaching activities. At that time, the Florentine cultural environment was lively but stiffened by the academic architectural language. So, during the late 1960s, Giorgini left Italy for the United States, where he became a lecturer at the Pratt Institute in New York. However, it was in the Gulf of Baratti, a marvellous stretch of Tuscan coastline, that Giorgini produced the two significant works, Casa Esagono (1957) and Casa Saldarini (1962), which best express his research. Despite the coldness reserved for him by his contemporaries, his entire life's work is now subjected to a renewed interest, and the two houses are placed under a magnifying glass.

Giorgini is familiar with the MERO component created by engineer Max Mengeringhausen, and with the connecting joints designed by Konrad Wachsmann for the US Air Force. He ponders the hexagonal model of Buckminster Fuller's Dymaxion House of 1929 and is aware of the design path of some of the most innovative architects, engineers and artists of the time, such as Frank Lloyd Wright and Le Corbusier. The prefabricated modular elements of the Casa Esagono arrive on-site ready for installation (Fig. 1).

Figure 1

Giorgini meticulously studies the individual prefabricated elements, the system of joints, the hinges connecting the pillars to the plinth, systematically conceiving the entire structure, and getting even to design the individual interior furnishings. Casa Esagono is the forerunner of the large-scale design phase, coinciding with the US period, in which Giorgini worked diligently on conventional systems [1]. The layout is a weave of hexagonal modules, reminiscent of a molecular structure or a beehive, in which six of them are arranged around the central one, connected by skilful joints. The central module serves for several functions: as an entrance, as an internal balcony overlooking the stairs, and as a hallway-distributor for the various rooms [7]. A few steps from the Casa Esagono, Giorgini built the Saldarini House, later called the Whale house because of its zoomorphic appearance, where he applied the study of morphology in the natural sciences to architectural design. The two houses form an organic part of the landscape. Both are suspended from the ground, which is barely furrowed by light supports, as a sign of deep respect for the mother earth on which they are built.

Giorgini sold Casa Esagono in 1969, the year he decided to move to America. Over time the house underwent a series of vicissitudes. The furnishings were lost during the 1980s when the ownership passed to the Municipality of Piombino, which handed it over for management ten years later. During this period, the structure underwent a series of heavy modifications. These included the application over all the façades of a plywood cladding nailed directly to the original light-coloured wood panelling and the subsequent application of a dark-coloured impregnating agent. In addition, metal props were inserted to support the floor without any plausible reason. In 2004, the corrugated steel roofing was repaired because of its serious state of corrosion, copper flashings were installed on the pillars and some repair works were carried out on the deteriorated steel components exposed outdoor.

It is only in recent years that the Esagono has found a new life. In 2013, the Municipality of Piombino handed over the building to the B.A.Co Baratti Architettura e Arte Contemporanea association, which is also the custodian of Vittorio Giorgini's archives, and takes care of the house and uses it as a venue for exhibitions and cultural events. The latest interventions on Casa Esagono date back to 2019 with the replacement of the metal props of the attic and the local repair of the roof damaged by the wind. Following further wind damage, the roof underwent a more extensive repair work in 2021, with the complete replacement of the roof covering.

A detailed geometric survey of the house was carried out verifying, by direct measurements, the dimensions of the whole house and of each of its components on the base of the drawings of the executive project stored in the Vittorio Giorgini Archive. An extensive photographic survey was also carried out. The results were several survey drawings (plans, elevations, sections, details) in scale from 1:25 to 1:10, including exploded axonometric views to better understand nodes and connections between each structural component.

The foundation consists of six reinforced concrete hexagonal-shaped plinths, each placed on a concrete slab. A special steel joint connects each plinth to a mushroom pillar, composed by four L-shaped wooden elements radially disposed. The joint is composed by three elements welded together: a hexagonal base, a sphere, and a cruciform element where the lower extreme of the four L-shaped elements converge (Fig. 2).

Figure 2

The first-floor slab is composed by seven hexagonal modules. Each module consists of a wooden structure composed of main beams, secondary beams and edge beams connected by steel joints, and a deck of nailed wooden staves arranged following a concentric hexagonal pattern. Each module has the same scaffolding, except for the central one, where the helicoidal stair is placed. The access to the main floor is through a trapdoor in the floor slab. The hip roof structure is made by a complex system of trusses arranged radially around a central hexagonal drum. Simple wooden planks and corrugated metal sheets complete the roof structure. The windows of the house, with single sash opening and sliding shutters, are located in the special box-shaped structures projecting outwards the external perimeter. Further box-shaped structures are used as storing spaces.

The ceilings of each module are made of wooden staves arranged similarly to the floor following a concentric pattern, except for the central hexagon which has main and secondary beams arranged orthogonally surmounted by wooden planks (Fig. 2).

The cladding intervention in the 1990s, beyond making the house look very differently than in the historical photos, makes it impossible to verify the state of conservation of the perimeter walls, which should be assessed after the removal of the plywood panels. From what could be observed, the two main problems with the house structure are the loosening of several joints at the main floor slab perimeter, where some past temporary repairs are visible, and the advanced state of corrosion of the stairs structure and the floor slabs bolted joints, due to the exposure to the coastal environment. The joints between the plinth and the pillar, instead, are in good condition thanks to the protective paint layers applied. As for the interior, Casa Esagono is almost bare of most of its original furnishings. The interior cladding shows chromatic alteration, stains and deformations of varying degrees caused by humidity, which in some cases have led to cracks. The ceilings show dark stains due to water infiltration. The floorings, near some of the structural joints, shows deformations and rotting due to incoming moisture caused by the same loosening of the joints. Over the years, some degraded parts have been replaced, in particular, wall panels, some doors and windows (Fig. 3).

Figure 3

Diagnostic investigations will clearly be required to understand the condition of the concealed parts.

Based on the analyses carried out on Casa Esagono and based on the state of the art [8], which included an in-depth examination of restoration works carried out on 20^th century wooden architectures, a targeted conservation approach was defined, based on maintaining the largest percentage of original elements in place through their restoration, while increasing their durability in view of the aggressive coastal environment. This approach involves the treatment of each element through customized and pre-tested restoration techniques, so as to intervene consciously and in proportion to the actual state of conservation of each part. Only in the most serious cases of deterioration the removal and replacement are accepted, replicating the elements in terms of materials, form and finish. The restoration process, therefore, involve both on-site and in-lab operations, where the elements previously catalogued will be transported.

After the realization of the 2D survey drawings and the visual analysis of current conditions, an Excel file was created for each of the building components (foundation, load-bearing structure, vertical connections etc.) reporting the following information: the type of element, the materials, the list of maintenance or recovery operations carried out over the years (if any), the list of degradation phenomena with description and indication of the operations necessary for recovery (Fig. 4).

Figure 4

Then, the 2D survey drawings were imported as an external file in DWG format, into Graphisoft ArchiCAD24, providing the basis for the 3D modelling of the building. The main tool used for the creation of the 3D elements was Morph tool of the Design menu and all the related tools. Each element was modeled as an individual element or as an Object (union of several Morph elements); this choice was considered on the basis of the recovery interventions foreseen for each element. The necessity of a partial disassembly of the structure, consequent to the defined intervention strategy, and therefore the need to perform a preliminary cataloguing and numbering of the components, finds in H-BIM an ideal support for the management of this phase [9]. In this way, each real component of Casa Esagono structure have a virtual correspondent in the 3D model, thanks to which it is possible to describe its current conditions and all the necessary conservation interventions. For cataloguing the house components, a method has been proposed that indicates, for each element, the coordinates of the position. The same morphology of the house, indeed, suggests the possibility of cataloguing the elements referring to the hexagonal modules of which they are part, numbered clockwise and assigning “0” to the central hexagon. Based on this macroscopic subdivision, it has been possible to assign an Identification code to all the elements (Fig. 5).

Figure 5

Therefore, the identification code of each element generated by default was modified accordingly under ID Properties. At the end of the modelling and cataloguing phase, we proceeded with the “computerization” of the elements. Graphisoft ArchiCAD24 allows to assign some predefined information in the ID and Properties list. However, the software also offers the possibility of modifying or adding new properties that can be assigned through by Properties Manager of the Options menu. Referring to the case study, to optimize the management of recovery interventions, new groups and properties have been created concerning the current state of conservation of the elements and the necessary recovery interventions. In the Existing State group, the properties created are related to Materials and Deterioration Types.

In the Conservation Intervention group, the properties created are related to the intervention necessary to carry out the restoration of the element and are subdivided according to the material (Wooden elements, Metallic elements, and Reinforced concrete elements) [10]. Once the necessary information has been assigned to the elements, it is possible to create specific Schedules by Settings Option in Document field. By querying the model, it is possible to extrapolate from the Schedules all the information associated with the elements with the possibility of modifying and/or updating them. In this way, it will be possible to create targeted lists according to the needs, such as filter and quantify all the elements that require a particular intervention.

Finally, we would like to emphasize one of the advantages offered by the H-BIM methodology: the interoperability, that defines the ability of a system or an IT product to cooperate by exchanging information with other systems or products in a more reliable and resource-optimized way. The model can exchange information on the Graphisoft ArchiCAD file with other software improving data management. With Export Property Values from Schedules (File menu, Interoperability subgroup Element Properties), it is possible to make the information in the Interactive Board to interact with an Excel spreadsheet [11], which allows for optimal data management in a more efficient way than the Schedules offered by Graphisoft Archicad. A further advantage is the possibility of managing the IFC (Industry Foundation Class) data of the model. The IFC is the international standard for exporting and sharing information contained in BIM models with different software, allowing the possibility of querying the elements by quickly selecting only those of interest thanks to an intuitive graphical interface [12].

The research study presented intends to demonstrate the possibility of carrying out the restoration of this architectural masterwork that, due to its constructive features, has always raised great questions about the technical feasibility of such an intervention.

At the same time, this work contributes in an original and innovative way in the broader field of H-BIM research from a methodological perspective, by emphasising the need of developing case-specific workflows and H-BIM models depending on the features of the case study, as well as in the field of built heritage conservation, by identifying and addressing the highly specific challenges that the case study, as a 20th century heritage building, arises.

Thanks to the support of the H-BIM model, it is possible to realize a sensitive and sustainable restoration of Casa Esagono. The final result will be the creation of a virtual archive of the building complete and updatable thanks to which, it will be possible to filter and extrapolate in a targeted manner the necessary data for the estimation of costs or raw materials to be used in the conservation works, allowing to save both materials and financial resources.

The use of a H-BIM model, therefore, revealed to be the ideal tool to manage the entire restoration process, whose ultimate goals are to exploit the potential of the house as a cultural attraction, capable of attracting visitors far outside the local context, and to celebrate and preserve Vittorio Giorgini's work.